Two months in Coz would send me off the tracks. I could stand two months in Roatan... well, I guess I have
Since you are talking about spending two months, I would wager that you will be diving from West End and the numerous day-dive ops that dot the landscape.
This area is radically different from the South side~ where you will find that perfected buoyancy, observational skills and patience pays off with great rewards. Small stuff hiding in the shallow, sunlit walls.
The North and West zones are a little deeper, darker and more rugged. With the local Conservation Zone in that area, you will see larger Fish and Crustaceans.
If "viz" is your thing, then no, Roatan will be a disappointment. However, if "viz" is your thing, a lot of very cool dive destinations will be a similar disappointment. Viz is highly over rated.
Coz is clearer for the same reason you do a lot of drift dives. Current.
In Coz, you may well see more pelagic creatures, but at a distance. With lessened viz, they are more susceptible to your getting ever closer to them. A bit of a trade-off.
Honestly, if your "dive count" is accurate at 25~49 dives, I think you will be well amazed at what a good DM can show you on Roatan.
If you are comparing videos and thinking that this represents reality... unlikely. There are some excellent videos out there that have made a silk purse out of a sow's ear. I have also recently seen some videos of my favorite dive on Roatan, presented by a dive op as a sales tool, that made the place look like death warmed over. Videos can be misleading.
I haven't been to Coz in many years, and I am really in no rush to go back~ certainly the lure of the bar scene and night life are no draw to me. I never thought that the diving was all that, even 15 years ago. My friends that still swoon for the place are gung-ho divers, but they also can be found slumped at the bars come closing time. Me? I'd rather be night diving.
You're just starting out at this, you've done Coz and gotten a glimpse of Belize... knock your socks off, go for it. Roatan will be something you'll wish to do sooner or later.